Polymeric materials, referred to hereinafter by the generic term "plastics", account for about 7% of municipal solid waste and up to about 20% of the waste by volume. This amounts to about 10 to about 12 million tons per year in the United States. Although plastics recycling is increasing, reprocessing and recycling generally requires segregation by type of plastic. Consumers, in general, and reprocessors often have no idea as to the composition of individual plastic articles. Consequently, processes for utilization of mixed plastic waste, particularly polystyrene, polypropylene and polyethylene, are urgently needed. The present invention provides a process for conversion of mixed plastic waste materials to a high quality synthetic crude oil which can be separated by fractionation into gasoline, diesel fuel and gas-oil components suitable as a feedstock to a catalytic cracker without additional treatment. As used herein, the term "municipal waste" includes all forms of polymeric containing waste materials which require or will benefit from recycling, including processing scrap, municipal waste and recovered or recycled polymeric materials.
U.S. Pat. No. 4,724,068 to Stapp describes a process for hydrotreating hydrocarbon-containing feed streams, especially heavy oils. The process of the Stapp patent utilizes a polymeric treating agent for upgrading the composition of heavy oils. In accordance with the process, an upgrading process is provided comprising the step of contacting (a) a substantially liquid hydrocarbon-containing feed stream substantially simultaneously with (b) free hydrogen, (c) hydrogen sulfide and (d) at least one polymer selected from the group consisting of homopolymers and copolymers of olefinic monomers, in the substantial absence of a solid, inorganic cracking catalyst and a solid inorganic hydroconversion catalyst. The process is performed under conditions so as to obtain a product stream having higher API.sub.60 gravity and having a lower content of hydrocarbons boiling above 1000.degree. F. than the feed stream.
In accordance with the process of the Stapp patent, impurities contained in the hydrocarbon-containing feed stream are at least partially converted to a "sludge", i.e., a precipitate of metals and coke, which is dispersed in the liquid portion of the hydrocarbon-containing product stream. The sludge and the dispersed olefin polymers are then separated from the liquid portion of the hydrocarbon-containing product stream by any suitable separation means, such as distillation, filtration, centrifugation or settling and subsequent draining of the liquid phase. The hydrocarbon-containing product stream has an increased API.sub.60 gravity and lower content of heavy fractions. The weight ratio of olefin polymer to hydrocarbon-containing feed is described as being generally in the range of from about 0.01:1 to about 5:1, preferably from about 0.02:1 to about 1:1 and more preferably from about 0.05:1 to about 0.5:1. The Stapp patent generally describes a procedure for hydrovisbreaking a heavy oil with a mixture of hydrogen and hydrogen sulfide in the presence of olefin polymers followed by recovery of an improved hydrocarbon oil product after separation from the olefin polymers.